Windows 7: System Keeps rebooting when External Hard is attached to it

Hello,

I have 2 External hard and When they are attached to computer with the USB cable, system keeps rebooting and won't come up so I have to unplug both of them and then system will boot up.
Any help would be great.

Thank you.
~0UnknowN1



EDIT (SOLUTION):
Thanks to experts in this topic and this forum here is the solution:

If anyone have this problem try to disable "Legacy USB". It is in your BIOS feature.

Thanks again. These experts are awesome.

When you have them both attached, Boot up and then go into BIOS and make sure the correct hdd is selected to boot first.

Not sure if that is your issue or not.

Questions.
1. What is on these hard drives?
2. If you only plug one in does it cause the same problem?
3. What is the boot order in your bios?
5. What does (system keeps rebooting and won't come up) mean?
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Thanks for the reply.
1.
In the first drive I have My "Documents, Music, Picture and Video Games"
In the second drive I have only "Videos"
2.
When I plug the first one the system Reboots 2 or 3 times and then comes up.
When I plug both of them it keeps rebooting and won't come up.
When I plug the second one the system keeps rebooting and won't come up.
3.
Hard Disk Boot Priority is (When both of the Hard Disks are unplugged):
1. Bootable Add-in Cards
2. Ch0 M. : ST3500320AS
Hard Disk Boot Priority is (When the first one in plugged)
1. Bootable Add-in Cards
2. Ch0 M. : ST3500320AS
3. USB-HDD0 : Hitachi HDS721010CLA33
Hard Disk Boot Priority is (When the second one in plugged)
NOTHING, I CAN'T GO TO BIOS SETUP (The keyboard won't work, I have two keyboards that one of them use USB and another one uses PS/2 to connect to the computer and both of them will not work.)
Hard Disk Boot Priority is (When both of the Hard Disks are plugged)
NOTHING, I CAN'T GO TO BIOS SETUP (The keyboard won't work, I have two keyboards that one of them use USB and another one uses PS/2 to connect to the computer and both of them will not work.)
4.
It means it keeps restarting.
The motherboard picture comes up and then restarts and again and again ... .

My system Specs:

Motherboard: Gigabyte EP43-DS3
CPU: Intel Core 2 Duo E8400 3.0GHz
RAM: 4GB
OS: Windows 8 RTM Professional(Build 9200)
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Thank you.
~0UnknowN1

I'm thinking that bootable add in cards as your first boot is the problem. Two ways most boots are set up.
1. Drive where operating system is located first boot, (in most cases C on disc 0, zero).
2. DVD/CD drive first boot and drive with operating system as 2nd boot.
Your computer is trying to boot from your external drives.
I have never used a Gigabyte motherboard so I really don't know it's bios setup procedure or terminology.

I have uploaded some images so could you explain more specifically


Thank you.
~0UnknowN1

Usually you can change the order by pressing + or - on your keyboard, or it will say a different value on the right to change order.

You need to move 2. Ch0 M. : ST3500320AS to the 1. position.

Then press ESC to exit, and when in Main screen ' SAVE and EXIT' or hit F10

Their be more than one place your have to select boot order. My Asus board is that way. I will let the Gigabyte people help you from here.

I moved it but still nothing happens, it keeps rebooting.When I put the first boot device to "CDROM" the computer boots up but when the second drive is connected it won't even in "CDROM" boot.

Thank you.

Did these drives boot ok with Windows 7, or what did you have installed before Windows 8 RTM?

Also are you able to connect the drives once you are booted.

Can you then go to Control Panel>Administrative Tools>Computer Management>Disk Management
Then take a screen shot, or look to see which drives show as Boot, or Active.